1. Field of the Invention
This invention relates to sewing machines and more particularly to a carpet sewing machine with twin feed rollers having a pivot point between the rollers to better feed the material to be sewn to the sewing machine.
2. Description of the Related Art
Twin roller feeds for material have been used in sewing machines. The twin rollers are synchronized to rotate together and both engage the material to be sewn, such as carpeting, at the same time. The rollers are fixed at the same height and both rollers travel up and down at the same rate. Problems arise when the material to be sewn is of uneven thickness since one roller will be pressing down on the material too hard and apply too much force on the material while the other roller is floating above the material providing little or no traction, thus causing bunching of the material between the rollers. This may cause an uneven feed resulting in jamming or uneven stitching.
Some twin roller feeders have two sets of gears and clutches which have to be synchronized to drive the rollers at the same speed in order to try to provide the same force on the material by the front an rear rollers. The separately driven rollers require separate gears and clutches which take up space and therefore space the rollers further apart. As the rollers are moved further apart the material being sewn is not as easy to turn in the sewing machine making it more difficult to sew along curves or around corners. Thus the operator may have to stop sewing and lift the twin rollers off the material to turn the material and lower the twin rollers back down on the material before commencing sewing. Further, separately driven rollers when not properly synchronized with cause bunching and jamming of the material due to uneven roller speeds.
The standard double roller sewing machines require the pressure of the spring pressing down on the double rollers and the height of the double rollers to be constantly adjusted for thicker material or a thinner materials or materials with different durometers to increase or decrease the optimum downward pressure of the double roller on the material being fed into the sewing machine. The operator will have to make these adjustments for every different material being sewn. Thus with the current double roller designs the rollers have to be lifted up and then placed on top of the material to be sewn when the material is fed into the sewing machine. The rollers have to be set at the proper height for each new thickness or durometer of material fed into the sewing machine. Further, the registration spring has to be calibrated for each different high or durometer of material fed into the sewing machine to provide the correct pressure of the rollers on the material.
Another problem with prior art double roller designs is that the extra clutches and gears increase the complexity and cost of the sewing machine and make the machine less robust because the added clutches and gears add more parts, which can fail reducing the reliability of the sewing machine.